The alternator stator of low power, such as is used in the equipment of motor vehicles, is usually formed by a stack of crownlike thin sheets, whose internal cylindrical face is equipped with notches intended to receive the phase windings, which generally number three. The most widely used windings of alternator stators of this type are either formed by coils closed on themselves and crisscrossed which encircle the poles, or of the so-called "undulating" type, known for example from French Pat. Nos. 1532522 and 2408937. It is the making of this latter type of winding which relates, more particularly, to the process of the present invention.
The windings considered here are either made "in situ," i.e., in the stator itself, by special machines, or formed externally of the stator and then placed in the notches of the stator. In a general way, these processes of making the windings are quite slow and therefore costly, because numerous long and complex operations are necessary. In both cases, the "rectangular" or "lengthwise" shapes of the coils or loops of the winding impose accelerations and decelerations during the process of mechanical shaping and results in a wire drawing effect, varying with the shape and tension given to these wires. To limit this drawing, it is necessary to reduce the speed of the machines used. Furthermore, this drawing makes it very difficult to use wires especially of aluminum or light alloy, which can withstand only a slight drawing.
Furthermore, the known process which involves shaping the coils externally of the stator, then inserting them into the notches, is difficult to use in the case of alternator stators with small inner diameters, because it is necessary to accomodate, on the inside of a free space of a very limited diameter, the whole of a complex equipment for preforming winding and/or expansion which again complicates the machines and increases their cost and fragility.
Moreover, the known processes which have just been mentioned make it difficult, or at least uneconomical, to make stators with separate phase windings; actually, in this case it is necessary to use a separate machine for each kind of winding and also to transfer the stators during the manufacture from one machine to another.